Flocculation by methylamine-epichlorohydrin polymer

ABSTRACT

A cationic, water-soluble, storage-stable, methyl-amineepichlorohydrin polymer is prepared by reacting a quantity of a methylamine-epichlorohydrin polymer which is well below its gel point with successively added small amounts of epichlorohydrin until the polymer nears the stage at which it is an irreversile gel, and then reacting the polymer with sufficient methylamine to inactivate substantially all amine-reactive epichlorohydrin residues present. At least the last step of the reaction is performed at a temperature at which a partial depolymerization of the polymer occurs. Water-soluble polymers of higher molecular weight and larger dimensions are produced by graft polymerizing one or more watersoluble vinyl monomers upon a hydrophilic water-dispersible cationic poly(hydroxyalkylene) polyamine, which is not necessarily the foregoing polyamine. The polymers are flocculants for suspended solids in sewage and mine effluent water and dry strength agents for paper.

United States Patent 91 FLOCCULATION BY METHYLAMlNE-EPICHLOROHYDRINPOLYMER [75] Inventor: Daniel Elmer Nagy, Stamford, Conn.

[73] Assignee: American Cyanamld Company,

Stamford, Conn.

[22] Filed: Dec. 8, 1970 [21] Appl. No.: 96,192

Related U.S. Application Data [62] Division of Ser. No. 778,934, Nov.26, 1968, Pat. No.

[ Aug. 28, 1973 Priniary Examiner-Samih N. Zaharna AssistantExaminer-Thomas G. Wise Attorney-Evans Kahn 5 7] ABSTRACT A cationic,water-soluble, storage-stable, methylamine-epichlorohydrin polymer isprepared by reacting a quantity of a methylamine-epichlorohydrin polymerwhich is well below its gel point with successively added small amountsof epichlorohydrin until the poly mer nears the stage at which it is anirreversile gel, and then reacting the polymer with sufiicientmethylamine to inactivate substantially all amine-reactiveepichlorohydrin residues present. At least the last step of the re- [52]U.S. Cl. 210/54 action is performed at a temperature at which a partial[51] Int. Cl...; I C021) 1/20 depolymerizafion of the polymer occurs,[58] Field of Search 210/10, 52-54 watebsoluble polymers of highermolecular weight I and larger dimensions are produced by graft [56]References Cited polymerizing one or more water-soluble vinyl UNITEDSTATES PATENTS monomers upon a hydrophilic water-dispersible 2,735,3727/1956 Lundberg 260/501 cationic poly(hydroxyalky1ene) polyamine, whichis 2,922,768 1/1960 Mino et al. 260/ 17-4 not necessarily the foregoingpolyamine. The polymers 3,248,353 4/1966 Coscia 260/292 are flocculantsfor uspended olids in ewage and mine 3,314,897 4/1967 Gaertner 260/2effluent water and dry Strength agents for paper 3,493,502 2/1970 Coscia210/54 5 Claims, 1 Drawing Figure 70 ,9 q N b u b 50 D Q k a I Q 50 Q Lu s 40 X k e g 30" k) 2 200 REACT/0N 7'/ME, HOURS 'mmznmaa ms \MQEQQMM(bu QQQMC \ftmbhi REA 6 T/OIV TIME, HOURS INVENTOR. DAN/EL ELMER M46) BY3 ATTORNEY FLOCCULATION BY METHYLAMINE-EPICHLOROHYDRIN POLYMER This is adivision of my copending application Ser. No. 778,934, filed on Nov. 26,1968, now U.S. Pat. No. 3,567,659.

The present invention relates to the flocculation of suspended matter inaqueous media by the use of hydrophilic, water-soluble orwater-dispersible, cationic, storage-stable methylamine-epichlorohydrincondensation polymers including water-soluble or. waterdispersiblecationic copolymers prepared by a graft polymerization of water-solublevinyl monomers upon hydrophilic water-dispersible cationicpoly(hydroxyalkylene) polyamines (including saidmethylamineepichlorohydrin polymer).

Modern systems of sewage treatment have created a great demand foreffective and efficient precipitation agents for the dispersed solidmatter therein, and modern systems for the purification of water requiresimilar agents for the precipitation of the organic and inorganic solidscommonly present in potable water. In such waters the weight of thesolid matter present is very small compared to the weight of the waterso that large volumes of water must be separated from small weights ofsolid matter. In the past such separation has been slow, difi'icult andcostly.

A major advance in the foregoing arts occurred when it was found thatthe water-soluble cationic polymer formed by reacting methylamine withepichlorohydrin in one step as disclosed and claimed in copendingapplication Ser. No. 706,592, filed on Feb. 19, 1968 by A. T. Coscia,now U.S. Pat. No. 3,493,502 possessed the property of flocculatingsuspended solids in aqueous media and thereby increasing the speed withwhich such suspensions could be settledand filtered. This polymer ischemically unstable and sets to a gel unless stored at low pH.

It has now been discovered that the polymer which is obtained whenmethylamine is reacted withepichlorohydrin in accordance with thecritical limitations hereinafter set forth, possesses in preferredembodiments the following preferred properties:

1. It is stable indefinitely in aqueous medium at normalstoragetemperatures, up to at least l50F.

2. Eachcomponent of the polymer the -N-amine units and the-CH,CH(OH)CH,- hydroxypropylene units) is strongly hydrophilic so thatthe polymer is water-soluble when having a molecular weight up to1,000,000 or more.

3. It is an active substrate for ceric ion-catalyzed graftpolymerizations, and long vinyl chains can-be formed thereon. Graftpolymers produced by this reaction are unusually effective flocculantsand dry strength agents for paper.

The aforesaid stable methylamineepichlorohydrin polymer is prepared by aprocess which comprises several steps.

In the first step, one mol of methylamine is reacted in aqueous alkalinesolution with an amount of epichlorohydrin (0.8-0.9 mol) which is closeto but safely (e.g., about 0.1 to 0.2 mol) short of the amount whichwould produce an irreversible gel. In this step sufficient time isallowed so that substantially all of the epichlorohydrin reactsbifunctionally with the methylamine. When performed in an open vesselthe mixture is maintained at low temperature to prevent volatilizationof methylamine, after which the temperature is allowed to rise to atemperature at which bifunctional reaction of epichlorohydrin goes tosubstantial completion.

In the second step the polymer is reacted at a pH above 8 with smallamounts of epichlorohydrin (e.g., about 0.05 0.005 mol ofepichlorohydrin per mol of methylamine originally taken) at spaced timeintervals until the polymer has advanced close to the point of ir'reversible gelation. A sufficient interval of time (3 to 10 minutes) isallowed to elapse between the addition of each increment ofepichlorohydrin so that each increment of epichlorohydrin reacts almostcompletely bifunctionally before the next increment is added, asevidenced by the viscosity of the solution becoming substantiallyconstant between each addition. It is difficult to cause all of theepichlorohydrin to react bifunctionally and hence the polymer in thisstep contains a small amount of amine-reactive epichlorohydrin residues.In the third step the epichlorohydrin substituents attached to thepolymer (and any free epichlorohydrin in the solution) are inactivatedby reaction with a watersoluble primary or secondary amine aspolymerization terrninators. The resulting polymer is storage-stable andis then ready for use.

The amine (hereinafter termed amine terminator) also controls the extentof the depolymerization reaction, and if the amount of this amine is toolarge in any instance, the molecular weight of the polymer will be toolow unless the reaction is quenched by cooling or otherwise in advanceof complete reaction of the amine. The amount of amine needed in anyinstance depends upon the number'of epichlorohydrin residues in thesolution, the functionality of the amine (whether primary or secondary),and on the number of quaternized nitrogen atoms in the polymer. Asuitable amount of amine is that which is sufficient to prevent thepolymer from gelling during further heating or on storage. Afteraddition of the amine the polymer solution is maintained at adepolymerization temperature at least until the polymer has becomestorage-stable. Further heating may cause additional depolymerizationand is within the scope of the process.

The amount of amine terminator needed in any instance for one of thesepurposes cannot be readily calculated, but can be found by laboratorytrial. In our work so far, 1 to 2 mol percent of the amine (based on thenumber of mols of epichlorohydrin taken) has been sufficient to preventgelation and produce very satisfactory polymers which arestorage-stable.

The depth of the decline in viscosity which occurs after attainment ofmaximum viscosity (section E) may be more or less than that shown in thedrawing, depending on the amount of amine terminator added and length oftime the solution is maintained at depolymerization temperaturethereafter. With careful control of the amount of amine added and theduration of heating, it is possible to inactivate the epichlorohydrinresidues and to terminate the polymerization reaction while the polymersolution is close to the gel point without significant subsequentdecline in viscosity.

In most polymerizations which have a gel endpoint it is common practiceto decrease the temperature of the reaction mixture as the gel point isapproached so as to retard the rate of reaction when the viscosity isincreasing most rapidly and thus permit the reaction to be safelyterminated close to but short of the gel point. We

have discovered, however, that in the reaction of the present inventionthe gel point can be safely approached at high temperature, providedthat the temperature is sufficiently high. We have found that safetemperatures lie within the range of 70C.-100C.

The reason why temperatures in this range are safe has not beenascertained. We have established that heating the polymer at this hightemperature in the presence of amine terminator causes adepolymerization reaction which is generally sufficient to preventpassage of the polymer from water-soluble state into an irreversible gelstate, and to convert any reversible gel which has formed back intowater-soluble polymer state. The nature of the depolymerizationreaction, however, has not been ascertained. From the fact that itcauses a major decrease in viscosity of the polymer, often by 50 percentor more, we believe that the depolymerization reaction involves ascission of carbonnitrogen quaternary ammonium bonds (i.e., scission ofcarbon bonds which are attached to quaternary ammonium nitrogen atoms),with consequent conversion of quaternary atoms to tertiary state anddiminution in the number of cross-linkages in the polymer. The speed ofthe depolymerization reaction varies mainly with the pH of the solutionand temperature, the depolymerization being favored by high pH and hightemperatures. Suitable pH values and temperatures can be found bylaboratory trial, employing the methods shown in the examples below. Asa rule of thumb we have found that at about pH 9 a temperature of about75C. is satisfactory and that at about pH 8, a tempera ture of about95C. is satisfactory.

The depolymerization reaction, as far as we know, is not detrimental tothe efficiency of the polymer as flocculant or as dry strength agent forpaper. lts principal benefit is that it permits a high molecular weight,water-soluble, storage-stable polymer to be prepared close to its gelpoint while greatly decreasing the danger of formation of anirreversible gel, and facilitating the entire operation.

The product of the above-described process is largely composed of unitsof the formula but may contain a small proportion of cross-linkages ofundetermined formulae. The polymer is accordingly most convenientlydescribed in terms of its method of preparation. For convenience it issometimes hereinafter termed a poly(hydroxy-propylene)poly(methylamine).

The aforesaid poly(hydroxypropylene) poly(methylamine) and the graftpolymers thereof which are described herein below, in some instancesform clear solutions when dissolved in water. In other instances, theyform colloidal solutions, i.e., solutions which are iridescent oropalescent, resulting from the fact that the macromolecules therein areof colloidal or nearcolloidal dimensions and either at or close to theborderline which exists between water-solubility and water-insolubility.For convenience, in the specification and the claims all these polymersare designated as water-dispersible," it being understood that the termincludes water-soluble.

The reaction of the present invention tolerates the presence of othermaterials. Thus, up to about mol percent of the methylamine can bereplaced with other water-soluble primary amines, for exampleethylamine, propylamine, ethanolamine, cyclohexylamine, etc. withsubstantially the same results, and the resulting polymers are withinthe scope of the present invention.

Suitable water-soluble amines for stopping the reaction are ethylamine,piperidine, diethylamine, ethanolamine, dimethylarnine and methylamineitself. While secondary amines give better results methylamine givessatisfactory results and because of its prior use in the process, ispreferred.

The effect of the depolymerization reaction is illustrated by thedrawing, which represents a plot of the changes in viscosity (curve 1)and a plot of the changes in temperature (curve 2) which occur as afunction of time when methylamine and epichlorohydrin are reacted inaccordance with an embodiment of the invention in which theepichlorohydrin is added with about maximum rapidity. Curve 1 is dividedinto sections A F, as shown by the lettered dotted lines.

In section A, 0.9 mol of epichlorohydrin is added to 1 mol ofmethylamine in a jacketed kettle provided with stirrer and refluxcondenser over two hours. The temperature of the reaction mixture iscontrolled at 25C. to minimize volatilization of methylamine, but at theend of the period is allowed to rise to C. At the end of the secondhour, sufficient acid acceptor solution (concentrated sodium hydroxidesolution) is added to maintain the pH at above 8.5 during the remainderof the reaction. During most of this period the viscosity of thereaction mixture remains substantially constant. At the end of theperiod, reaction of the epichlorohydrin is substantially complete.

In section B, epichlorohydrin is added in increments of decreasing size,first of 0.01 mol and then of about 0.005 mol at intervals of about fiveminutes resulting in small stepwise increases in viscosity (shownschematically in drawing). At the end of the period of time covered bythis section the viscosity of the reaction mixture rises almostvertically, and addition of epichlorohydrin is stopped.

At the start of section C, sufficient methylamine is added (1% based onthe weight of the methylamine originally taken) to inactivate theamine-reactive epichlorohydrin substituents present and to inactivateany free (wholly unreacted) epichlorohydrin present, together with aquantity of cold water to slow the rate of viscosity increase. Themixture is heated back to 95C. The methylamine reacts as reactionterminator, and the depolymerization reaction begins. The methylamine isadded to provide an excess over the minimum needed to inactivate theepichlorohydrin residues. The methylamine does not react immediately,and the viscosity of the solution continues to climb. As a result of thedepolymerization reaction and inactivation of the residualepichlorohydrin the climb stops at a viscosity of about 95 seconds, atwhich point the polymer is close to its gel point. In section Edepolymerization is the only reaction which occurs, and the viscositydrops rapidly to about 30 seconds and levels off, as shown by theportion of the curve shown by dashes (section F). The solution is cooledto room temperature and is then ready for storage or use.

The solution obtained may be spray dried. The polymer is recovered as afree-flowing powder which dissolves readily in water. The solutionobtained by dissolving the polymer in water possesses substantially allthe properties of the solution prior to being spray dried.

The aforesaid polymer solution, as produced by the process outlinedabove, possesses desirable flocculating properties and is storage stableeven though containing polymer solids by weight and even though thepolymer is of high molecular weight and close to the gel point. Whenused as a fiocculant the polymer solution is advantageously diluted tol%5% concentration and is uniformly incorporated-into the suspension tobeclarified in amount sufficient to cause the suspended particles tocoalesce and precipitate. The proper amount varies from instance toinstance depending chiefly upon the zeta potential of the particles andthe cationic charge of the polymer andis most conveniently found bytrial on a sample of the suspension to be clarified; The polymersolution iseffective for the flocculation of the suspended solids insewage, mine effluent water and paperrnill whitewater. The pH of thesuspension to be clarified is not critical and may be in the rage of 410.

In the manufacture of paper the polymeris advantageously added to apapermaking furnish having a pH of 5-9, at the fan pump or similarlocation in an effective amount as dry strength agent. About 0.1% basedon the dry weight of the fibers is about the least amount which producesa significant strengthening effect, and more than about 3% on the samebasis does not produce commensurate increases in strength and so thisamount is regarded as the practical maximum. The suspension is formedinto paper in customary manner, and no special drying or other treatmentis necessary. The product is paper composed of cellulose or othernegatively charged fibers bonded together by an adsorbed content of thepolyamine.

Additionally I have found that valuable water-soluble cationic polymersof very high molecular weight, which may be therrnosetting, are producedwhen a watersoluble poly(hydroxy-alkylene) polyamine is graftpolymerized by the eerie ion method of Mino et al. US. Pat. No.2,922,768 with a water-soluble vinyl monomer or mixture of monomers. Ihave found that such graft polymers are thermosetting when thepoly(hydroxyalkylene) polyamine used as the substrate for the graftpolyermization is thermosetting. The polymers produced in this mannerare useful as flocculants and as agents which improve the strength ofpaper. They are employed in the same manner as heretofore knownpolyamine agents.

The substrate polymers used for the preparation of the graft polymers ofthe present invention contain -CH,-CH(OH)CH,-linkages and it is thoughtthat the presence of -0H substituents in these linkages is the reasonwhy the graft polymerization reaction proceeds with formation of suchsatisfactory products. The composition of the polymers is illustrated bythe instance where the storage-stable methylamine-epichlorohydrinpolymer of the present invention is the substrate; in that instance thegraft polymer hasthe theoretical formula:

cm on.

wherein the M's represent graft polymerized vinyl chains. It will beseen that the polymer vinyl chains are attached to the same carbon atomsto which the -OH substituents are attached.

The vinyl monomers which can be graft copolymerized include vinyl amidessuch as acrylamide, methacrylamide, dirnethyl aminoethyl methacrylate,and the like; vinyl acids such as acrylic and methacrylic acid; vinylnitriles such as acrylonitrile, methacrylonitrile and the like, andesters such a methyl acrylate, methyl methacrylate, and mixtures of suchvinyl monomers. Vinyl amides, particularly acrylamide, and mixtures ofacrylamide with one or more of the monomers listed above, are preferablebecause they produce a product which is highly water-soluble, whichpossesses excellent fiocculating properties, and excellent strengtheningproperties for cellulose paperrnaking fibers. Where the monomers arepresent, it is preferred that acrylamide be at least mol'percent of themixture. In every instance where the graft polymer is not subjected to asolubilization treatment the proportions of watersoluble vinyl monomerin the polymerization mixture is such that the graft polymerizationproduct is hydrophilic and water-dispersible as at least a colloidsolution.

Acrylonitrile and other vinyl monomers which produce insoluble graftcopolymer products can also be used to form thevinyl substituents of thegraft copolymers of this invention in which event the graft polymer issubjected to a solubilization treatment. For example, when acrylonitrilealone is the vinyl monomer to be polymerized, the graft polymer maybeinsoluble in water and if insoluble the polymer can be solubilized byhydrolysis of nitrile groups with alkali.

' T h e poly(hydroxyalkylenfipolyamines are highly receptive to graftpolymerization, and it is readily feasible to graft polymerize on thepolyamine substrates a weight of vinyl monomer which is many times theweight thereof. However, when the weight of the grafted monomer is morethan roughly 10 times the weight of the substrate the properties of thesubstrate nucleus tend to become masked and the properties of thepolymer are predominantly those of the grafted vinyl material.

about one-tenth and 10 times the weight of the poly{ amine, and weprefer the intermediate range of onehalf to 5 times the weight of thepolyamine.

The ceric ion catalyst is essentially a dilute aqueous acidic solutionof a water-soluble ceric salt. A 0.1 N solution of ceric ammoniumnitrate, ceric sulfate, ceric ammonium sulfate, etc. in l N nitric acidis satisfactory.

Only a small amount of ceric salt (from 1 to 10 X 10 mol per mol ofvinyl monomer) is needed and the polymerization proceeds at roomtemperature even in the presence of free (dissolved) oxygen. Very littlehomopolymerization occurs, and hence the amount of vinyl monomer whichis grafted is usually above 90% of the amount supplied to the reactionmixture.

The poly(hydroxyalkylene)polyamines which are benefited by graftpolymerization according to the present invention are water-soluble,preferably but not necessarily of high molecular weight, and have asubstantial content of hydroxy-alkylene linkages. They may but need notbe thermosetting, and, when thermosetting impart wet strength inaddition to dry strength. Their molecular size may range from the sizeat which they are composed of a few monomeric units to several hundredthousand or more. At least 10 mol percent of the alkylene unitsconnecting the amino-nitrogen atoms should contain at least one hydroxylsubstituent each.

Suitable poly(hydroxyalkylene )polyamines of the foregoing descriptioninclude the water-soluble thermosetting polymers prepared by reactingammonia with epichlorohydrin, by reacting a mixture of ammonia and awater-soluble alkylene-polyamine in 1:1 molar ratio withepichlorohydrin, by reacting a 6:1 molar ratiomethylaminezethylenediamine mixture with epichlorohydrin, by reactingmethylamine and epichlorohydrin as disclosed in said copendingapplication; by reacting a 1:1 molar ratio mixture of ammonia andguanidine with epichlorohydrin, and by reacting diethylenetriamine withepichlorohydrin. Detailed methods for the preparation of these and otherpoly(hydroxyalkylene) polyamines are disclosed in U.S. Pat. Nos.2,585,935 and 2,595,936, and Coscia U.S. Pat. No. 3,248.353. Suchpolymers can be prepared in nonthermosetting state by inactivating anyunreacted epichlorohydrin substituents present by adding dimethyl amineto the reaction mixture so that the polymeriza' tion process is haltedbefore the polymer has reached the gel stage.

The graft copolymerization reaction using amethylamine-epichlorohydrinresin is carried out at an acid pH,preferably at a pH of about 3 to and in the presence of sulfate ions.The pH of the reaction mass is initially adjusted to 5 or below beforeor immediately after addition of the catalyst. The pH is preferablymaintained below 5 but above 3 during the remaining course of the graftpolymerization reaction. it has been found that if the pH of thereaction mass is permitted to fall below 3, the conversion rate of thecopolymerization reaction is significantly lowered.

The graft copolymers of this invention can be of any desired molecularweight so long as they are soluble or dispersible in aqueous medium,within the pH range of 4 10.

The viscosity of solutions of the graft copolymers of this invention canbe reduced by the addition of small amounts of an alcohol, such asisopropanol, methanol, ethylene glycol, or propylene glycol. Theviscosityreducing agent is added to the reactants as disclosed in theaccompanying examples.

Concentrated solutions of high molecular weight graft copolymers of thisinvention can be, in some instances, quite viscous, and may even takethe form of firm gels. Such gels form mobile aqueous solutions ordispersions when stirred with several times their weight of water havinga pH in the range of 4 10.

The process for preparing the graft copolymers of the present inventioncan be carried out at temperatures between about 10C. and 90C. andpreferably at temperatures between about 25C. and 55C. Temperaturessignificantly above C. are preferably avoided because the exothermicreaction may proceed too rapidly at these high temperatures, and lead toslightly less effective polymers.

While this process can be carried out under pressure or partial vacuum,if desired, atmospheric pressure operation has been found mostsatisfactory.

The cationic amine-graft copolymer removal agents can be added to thewaste water system being treated in widely varying amounts, depending onthe degree of waste removal desired in the system. The amount of removalagent added can also vary with the nature of the treatment system, thatis, whether it is a primary or secondary treatment system, and with thepermissible dwell time in the system.

The cationic copolymer removal agents can be added to the waste watersystem in amounts from about 0.001 to about 5 percent by weight of thedispersed solids. Preferably, concentrations of removal agent in thewaste water system should be maintained between about 0.1 and 2 percentby weight of the suspended solids.

The invention is further illustrated by the examples which follow. Theseexamples are preferred embodiments of the invention and should not beconsidered as limitations thereon.

EXAMPLE 1 The following illustrates a preferred method for thepreparation of the methylamine-epichlorohydrin polymer of the presentinvention.

To 100 g. of methylamine (3.25 mols) dissolved in 400 g. of water in areaction flask provided with stirrer, thermometer and reflux condenseris added 260 g. of epichlorohydrin (2.8 mols, equivalent to 0.87 mol permol of amine) over 60 minutes cooling (by ice bath) being applied asnecessary to keep the temperature of the reaction mixture between25C.40C. at the first half of the reaction and at 50C80C. during thesecond half of the reaction. 160 g. of 36% aqueous sodium hydroxidesolution (1.44 mol) at C. is then added to the reaction mixture. Thereaction mixture is then heated to C. and epichlorohydrin is added in 1ml. (1/214 mol) portions and the viscosity of the reaction mixture isfollowed by filling a 6 mm. (inside diameter) vertical glass tube withthe hot solution and noting the number of seconds required for the levelof the solution to fall 13 inches when the bottom of the tube is opened.Results are as follows:

M1. Epi.

Temp. Viscosity C.

Time (Minutes)' Added (5 From start of reaction 0f reaction mixture, byglass tube method After 132 minutes, the reaction mixture becomes veryviscous and the viscosity continues to rise. There is then added 274 g.of cold water containing 0.8 ml. of methylamine as reaction terminator,and the reaction mixture is heated to 94C. The following viscositychanges occur:

Time Temp. Viscosity (Minutes) (C.) Seconds 1 7 94 48 220 94 90 250 94120 3 lo 94 l 36 345 94 I 605 94 60 From start of reaction Of reactionmixture by glass tube method The decrease in viscosity after 310 minutesis caused by scission of bonds within the polymer molecule.

The reaction mixture, which has a pH of 8.7, is cooled, acidified to pH6.3, and diluted with water. The product contains 19.3% polymer and hasa viscosity of 900 centipoises at 20C.

The solution is stable indefinitely at 70F. and 135F. both at pH 8.7 and4.5.

EXAMPLE 2 This illustrates the effectiveness of the polymer in Example las flocculant.

The apparatus employed consists of a No. 2 Biichner funnel having itsstem connected air-tightly to a volumetric cylinder through an adapterhaving a side-arm which is connected to a gauged vacuum source. A sheetof No. 2 Whatman filter paper is placed in the funnel over a wire-meshscreen support. For each test, a 300 ml. sample of sewage sludge (4.3%solids) is placed in a 400 ml. beaker. A 1% by weight solution in waterof the polymer of Example 1 is :measured into a similar beaker. Thesludge is then poured into the polymer solution and the mixture ispoured back and forth between the beakers three times to ensure completemixing. The resulting mixture (a conditioned sludge) is then poured intothe Biichner funnel (the filter paper in the funnel having beenpreviously moistened and applied under vacuum to form a seal). After5-10 seconds (to permit turbulence to cease) inches of vacuum is appliedto the funnel and the time required for 100 ml. of filtrate to passthrough the filter is recorded. The-test is repeated, the polyaminebeing replaced by a laboratory standard flocculant (flocculant C-3l ofthe Dow Chemical Co.) as control.

The filtration rate of the sludge treated with the polymer of thepresent invention is about twice as fast (2.04 times) as that of thecontrol.

EXAMPLES 36 This series of examples shows the effect of variations inthe amount of alkali added to the reaction mixture.

The general procedures of Examples 1 and 2 are repeated with variationsas follows. I

Example 3. Addition of the sodium hydroxide solution is commenced when34% of the epichlorohydrin has been added and is completed in 1.6 hours.The remaining 66% of the epichlorohydrin is added over two hoursstarting with the addition of the sodium hydroxide solution. Thesolution is then heated to 79C. After the odor of epichlorohydrin hasdisappeared from the solution, during the next 4 hours, a total of 27 g.of epichlorohydrin is added to the reaction mixture in l-g. portions.The viscosity of the solution is allowed to become constant between eachaddition. At the beginning of the 4-hour' period, the viscosity is suchthat one second is required for the solution to descend 13 inches 10 inthe glass tube. At the end' of the fourth hour 7 seconds are required,and no more epichlorohydrin is added. The viscosity climbs as follows.

Minutes After Last Addition Temp. Viscoigg 5 or Epichlorohydrin c. (Seco0f hot solution, by glass tube method After minutes the viscosity'isincreasing rapidly and gelation begins. At this time ml. of cold waterand 3.7 g. of 40% methyiamine are added and the reaction mixture isreheated and held at 75C. After 245 minutes gelation is reversed and theviscosity of the solution falls, owing to scission of bonds in thepolymer molecule and consequent depolymerization.

After 582 minutes the heating is discontinued. The resulting polymer iscooled and is storage-stable.

Examples 4-6. The general procedure of Example 3 is followed with thefollowing exceptions: (1) different amounts of alkali are used asrecorded in the table below, and (2) the temperature of the reactionmixture is maintained at 90C. during the incremental addition of l-g.portions of epichlorohydrin. In Example 6 alone, the alkali is addedconcurrently with the epichlorohydrin from the beginning of-thereaction.

The polymers prepared in Examples 3-6 are evaluated as sewageflocculants according to the procedures outlined in Example 2. Resultsare as follows:

Mols NaOH Mols Epi. Soln. Floc. Effic. Ex. Added Reacted' pl-l' ofPolymer 40 3 0.525 0.965 8.55 Sl. better 4 0.600 0.965 8.55 Do. 5 0.8101.02 9.05 Do. 6 0.900 1 l 8 9.0 Do. Per mol of methylamine Afteraddition of epichlorohydrin 45 Based on filtration rate produced bylaboratory standard flocculant EXAMPLE 7 Vise. After 12 Mos.

pH Temp. C.

1.3 25 No change 3.3 25 Do.

3.l 50 Do.

The results indicate that the polymer is stable indefinitely.

EXAMPLE 8 An aqueous solution corresponding to that prepared in Example1 containing 20% polymer by weight and having a pH of 6.3 is fed into alaboratory spray drier at the rate of 50 ml. of solution per minuteunder conditions such that the inlet air temperature of the drier is400F. and the outlet air temperature is 150F. The size of the sprayedparticles and the duration of the drying are such that the productcontains moisture by weight and flows freely when poured from acontainer.

The product is a free-flowing powder which dissolves rapidly in waterforming an opalescent solution therein. The resulting solution possessessubstantially the same efficiency as flocculant and as dry strengthagent for paper as the parent solution.

EXAMPLE 9 The following illustrates the ease with which the polymer ofthe present invention undergoes graft polymerization with acrylamide toform a polymer of high molecular weight. The ratio of the polymer to theacrylamide is 1:1 by weight.

To 85.6 g. of a 23.6% by weight aqueous solution of the water-soluble,stable cationic polymer of Example 1 having a viscosity of 244centipoises at 25C. are added consecutively 50 ml. of water, enough 50%11,80 to lower the pH to 4.8, 20 g. of acrylamide, 4 ml. of isopropylalcohol and sufficient water to increase the weight of the solution to188 g.

To this is quickly added with stirring 12 ml. of ceric catalystsolution, prepared by mixing ceric ammonium nitrate and concentratednitric acid in water to yield a solution 0.1 N with respect to ceric ionand 1 N with respect to nitric acid, as disclosed in said Mino et al.patent.

The temperature of the reaction mass rises to 52C. approximately oneminute after addition of the ceric solution, and the solution reaches ahigh viscosity in the first 2 minutes.

After standing overnight, the final pH of the reaction mass is about 3.2and the aqueous solution of the graft copolymer product has a viscosityof 7 70,000 centipoises at the concentration of 20% active solids, whichindicates that the molecular weight of the graft polymer is in excess of1,000,000.

EXAMPLES -12 The following shows how the viscosity (and thereforemolecular weight) of the graft copolymer can be controlled by varyingthe amount of alcohol.

The procedure of Example 9 is repeated except that the amount ofisopropyl alcohol added is varied as shown in the table below. Theresults show that the molecular weight of the graft copolymer decreasesas the amount of alcohol increases. The viscosities were determined onthe final solution at uniform solids content and at 25C.

M1. Visc.(cp) Example lsopropanol of Polymer 10 2 120,000 1 l 6 29.00012 5,500

EXAMPLE l3 The following illustrates the preparation of a polymersimilar to that of Example 9, except that the weight ratio of thepolymers is 3:1.

To 83.5 g. of a 24% solution of a methylamine epichlorohydrin polymerprepared by the method of Example 1 having a viscosity of 500centipoises are added consecutively sufficient 50% sulfuric acid toadjust the pH to 5.4, 60 g. of acrylamide, sufficient water to increasethe weight of the solution to 400 g., and 24 ml. of the 0.1 N cericsolution of Example 9 in one portion with stirring. An exothermicreaction occurs, and the solution becomes a finn gel having a final pHof 4.1. Water is added and the gel is stirred slowly. The gel dissolves.The resulting solution is diluted with water to 3% polymer solidscontent by weight and the resulting solution is viscous.

This solution is highly efficient as a sewage flocculant. In comparativetests, it is found that the optimum amount of the product of thisexample needed for effective sewage solids removal is only of the amountrequired of a commercial sewage flocculant. Further, water can befiltered through the sludge produced by the graft copolymer of thisexample three times as fast as it can be filtered through the sludgetreated with the commercial flocculant.

EXAMPLE 14 This illustrates the hydrolysis of an acrylamidegraftedpolyamine of the present invention to produce a polyarnpholytecontaining carboxy groups.

The procedure of Example 13 is repeated except that the amount ofacrylamide is increased to 100 g. (5:1 acrylamide:polyamine ratio). Thestarting graft polymer is a firm gel which is dissolved by slowlystirring into water at C. containing 2 mols of sodium hydroxide per molof combined acrylamide taken.

After 6 hours the mixture is a viscous solution which is dilutable withwater, but which precipitates when acidified.

EXAMPLE 15 The procedure of Example 13 is again repeated except that 20g. of acrylamide is used (1:1 acrylamide:- polymer ratio). After thealkaline hydrolysis, the resinous copolymer product is soluble in waterbut precipitates when the pH is lowered to about 5.0. The precipitatedresin is redissolved almost completely when excess acid is added.

EXAMPLE 16 The following illustrates the preparation of a polymeraccording to the present invention wherein the backbone ispolyacrylonitrile.

To g. of a 20% solution of methylamine epichlorohydrin cationic polymerhaving a viscosity of 504 cp. at 25C. is added sufficient 50% H,SO todecrease the pH of the solution to 3.9 and sufficient water to produce atotal solution weight of 1,300 g. The solution is sparged with nitrogenand 100 g. of acrylonitrile is added, followed by 15.5 ml. of the 0.1 Nceric solution of Example 9. Immediately after addition of the cericsolution, the reaction mixture warms and becomes cloudy and whitish, andthickens. After standing over night, the resinous reaction product isadded slowly to 118 g. of sodium hydroxide in 1 liter of water at 95C.Hydrolysis occurs with formation of carboxyl groups, as shown by theproduct becoming soluble in water. The resulting red solution becomescolorless and homogenous in about 2 hours. It is held at 95C. for atotal of 6 hours. A precipitate forms when the clear homogenous solutionis acidified.

EXAMPLE 17 The following illustrates the grafting of acrylamide andmethylenebisacrylamide upon a polyamine of the present invention.

To 432 g. of diethylenetriamine in 161 g. of water at 92C. is added 430g. of epichlorohydrin over a period of 2.5 hours. The solution becomesviscous and is diluted with water containing 100 ml. of 10 N sulfuricacid to yield a final solution comprising 1,462 g. of amine resin (48.2%of the weight of the solution). 41.5 g. is diluted to 20% solids byaddition of water, the pH of the solution is adjusted to 2.5 withsulfuric acid, and 20 g. of acrylamide and 40 ml. of a.0.1% by weightsolution of methylenebisacrylamide are added. To this solution is addedml. of the 0.1 N ceric nitrate solution of Example 9, and the solutionsets to a watersoluble gel almost immediately.

The solution is an effective flocculant for the solids in sewage.

EXAMPLE 18 The procedure of Example 17 is repeated except that only 20ml. of the 0.1% methylenebisacrylamide solution is used. The resultingcopolymer resin solution thickens but does not gel. The product is aflocculant but is considerably less so than the polymer of Example 17.

EXAMPLE 19 A water-soluble polyamidepolyamine is prepared by condensingadipic acid and diethylenetriamine in 1:1 molar ratio, and 0.3 mol ofepichlorohydrin is bifunctionally reacted therewith. The resultingcondensate is mixed with equal parts by weight of acrylamide and wateradded to dilute to 20% solids. Ceric nitrate catalyst solution is addedto catalyze the graft copolymer ization reaction as shown in Example 9.A high viscosity polymer results. This polymer is a dry strength agentfor paper.

EXAMPLE 20 The procedure of Example 9 is repeated except that 20 g. ofacrylamide l g. of acrylic acid are substituted for the acrylamide usedto form the vinyl substituent.

The graft copolymer is an effective precipitant for the dispersed solidsin sewage.

EXAMPLE 21 The procedure of Example 9 is followed except that 20 g. ofacrylamide l g. of dimethylaminoethylmethacrylate are substituted forthe acrylamide used to form the vinyl substituent.

The graft copolymer is an effective precipitant for the dispersed solidsin sewage.

EXAMPLE 22 The procedure of Example is followed except that g.methylacrylic acid are substituted for the acrylamide used to form thevinyl substituent.

EXAMPLE 23 The following illustrates how the viscosity of the graftcopolymer products of this invention and therefore the molecular weightof the product is afiected by changes in the initial pH of the reactionmixture. The materials used and the procedure followed are essentiallythe same as those of Example 9, above, except that no isopropyl alcoholis used. Results are as follows:

pH During Viscosity of Run Polymeriz. 5% Solution A 4.4 1500 Based on pHimmediately afier polymerization. The results show that the molecularweight of the graft polymer falls off sharply when the pH of thereaction mixture is allowed to fall below 4.

Of reaction product EXAMPLE 24 Filtration pH During Rate of PolymerPolymeriz. Sludge A 4.4 7.6 D 3.1 8.3 G 1.55 2.2

Based on filtration rate (taken as l) of sludge treated with laboratorycontrol flocculant The results show that the graft polymer produced atpH 3. 1 produced a sludge which filtered 8.3 times as fast as the sludgetreated with the laboratory control flocculant.

EXAMPLE 25 The following illustrates the manufacture of paper ofimproved strength by the use of graft polymers of the present invention.

The polymers are prepared by the method of Example 23, except that thepH values of the solution during the graft polymerization is as shown inthe table.

pH During Vise. of Polymer Polymeriz. 5% Soln(cp A 5.05 320 B 2.3 I 12 C1.9 D 1.1 56

Results are as follows:

Polymer Burst pH Dur.

Graft Vise. of 11 Run No. Polymer 5%Soln. Polymer Lb. lncr. 1 None 40.62 A 5.05 320 0.5 58.1 43.1 3 B 2.3 112 0.5 57.] 39.6 4 C 1.9 0.5 57.139.6 5 D H 56 0.5 52.8 30.0

The results show that the strength-imparting efficiency of the graftpolymer increases sharphy as its molecular weight rises.

EXAMPLE 26 This example illustrates a process for preparing the graftcopolymers of this invention in which the vinyl monomer and the cericcatalyst solution are incrementally added to the solution of thecationic aminecontaining polymer to permit convenient regulation of thepH and the rate of the exo-thermic reaction. To 171 g. of the 23.0%solution of methylamineepichlorohydrin condensate of Example 1 in aflask equipped with sparger, stirrer, thermometer and three droppingfunnels are added 40 ml. of water and the solution is acidified to pH4.05 with 50% aqueous H,SO The resulting solution is sparged withnitrogen.

Into the funnels are respectively placed 40 g. of acrylamide and 60 ml.of water; 24 ml. of the 0.1 ceric catalyst solution of Example 1 and 26ml. of water; and 10 ml. of 10% aqueous NaOH solution. One tenth of theceric catalyst solution and one-tenth of the acrylamide are first addedwhile continuing the nitrogen sparge. After about 10 minutes, 1 ml. ofthe NaOH solution is added and then another one-tenth portion of theacrylamide and ceric are added, followed by another 1 ml. of sodiumhydroxide. This sequence is repeated until all the materials have beenadded.

The amount of alkali added is regulated to keep the pH at 3.4. The finalsolution has a viscosity of 272,000 centipoises at polymer solids,indicative of a polymer having a molecular weight of more than1,000,000. Less viscous solutions can be prepared by the procedure ofthis example by adding small amounts of isopropyl alcohol to thereaction mixture.

The invention in its broader aspects is not limited to the specificdetails shown and described, and departures may be made from suchdetails without departing from the principles of the invention andwithout sacrificing its chief advantages.

I claim:

1. A process for clarifying an aqueous medium having solid mattersuspended therein, which comprises distributing through said suspensiona small but effective amount as flocculating agent for said solidmatter, of a hydrophilic water-dispersible cationicmethylamine-epichlorohydrin polymer which is storage-stable, prepared bya process which consists essentially in substantially completelyreacting in aqueous alkaline solution 1 mol of methylamine withepichlorohydrin in suffifient amount between 0.8 and 1.2 mol to producea polymer which is cationic and water-dispersible; reacting said polymersucessively, substantially but not completely, with increments ofepichlorohydrin each less than about 0.1 mol per mol of said methylamineat a pH above 8 until the polymer is close to but short of the point atwhich it becomes an irreversible gel whereby said polymer contains asmall number of aminereactive epichlorohydrin residues; adding to theresulting solution sufficient of a water-soluble primary or secondaryamine to preventsaid polymer from gelling during further heating and onstorage; and maintaining the resulting solution at a depolymerizationtemperature at least until the polymer therein has becomestorage-stable.

2. A process according to claim 1 wherein the pH of the suspension to beclarified is in the range of 4 l0.

3. A process according to claim 1 wherein the suspension to be clarifiedis sewage.

4. A process according to claim 1 wherein the concentration of polymerin the aqueous medium is between about 0.1% and 2% of the weight of saidsolid matter.

5. A process according to claim 1 wherein the flocculating agent is apolymer according to claim 1 which has been graft polymerized withbetween one-tenth and 10 times its weight of a water-soluble vinylmonomer in the presence of a ceric graft polymerization catalyst.

t a a t a UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 0 PatentNo. ,7 5,159 Dated August 28, 1973 Inventor) Daniel Elmer Nagy It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below: Q

Abstract line 6, "irreversile" should read irreversible CH 9 Column 1,line 44, "-N-amine" should read, N-amine Column 3, line 51,"poly(hydroxy-propylene)" should read polyflhydroxypropylene) Column 5line 37 "poly (hydro cy-alkyle'ne) should read poly (hydroxyalkylene)Column 8, line 42 "minutes cooling" should read minutes cooling Q Signedand Scaled this Thirteenth a 0 Jul [SEAL] v D V y f y 1975 Arrest.

:tUTH- C. MAISON C. MARSHALL-DAN! ffi Commissioner of Patent: andTrademarks

2. A process according to claim 1 wherein the pH of the suspension to be clarified is in the range of 4 -
 10. 3. A process according to claim 1 wherein the suspension to be clarified is sewage.
 4. A process according to claim 1 wherein the concentration of polymer in the aqueous medium is between about 0.1% and 2% of the weight of said solid matter.
 5. A process according to claim 1 wherein the flocculating agent is a polymer according to claim 1 which has been graft polymerized with between one-tenth and 10 times its weight of a water-soluble vinyl monomer in the presence of a ceric graft polymerization catalyst. 